Not so fast......
You have forgotten spruce, which is nearly as light as cedar, but considerable tougher, and yes, you can certainly make an excellent hardwood paddle (maple and ash absolutely, maybe white oak, cherry, etc. if you can find a good piece) BUT, like anything else - you have to know how. If you build the same paddle from these woods that you would make from cedar or spruce, it will be a heavy piece of junk. Back when Norm and I sold canoes, we used to call them "bear clubs".
Case in point....Here are two paddles about 51/2' long. On the left, is an Old Town spruce paddle from the early 1970s (back when their spruce paddles were excellent, and about as good as you could possibly buy in a one-piece paddle). At the time, their ash paddles were shaped very similarly and were tough, but borderline bear clubs in terms of weight and balance.
On the right is a maple paddle that I bought about 1975 for $25 from a starving hippy who walked into my store, looking to unload it for cash. It's without a doubt made by somebody with spar-making training and the nicest solid paddle I've ever seen. So far, nobody has been able to tell me who built it, but it is very old. The guide-style grip is actually a smoothed-out octagon with a little bulb on top and at the bottom of the grip area, the shaft has a small octagonal cross-section like a collar, which then becomes round. As you go down the shaft, it slowly turns into a long, fore-and-aft oval for your lower hand and about the time you get to the throat, it's become a fairly sharp rib that runs down the middle of the blade and slowly tapers out. The blade is very thin (like 1/4"-5/16" for a lot of it) and then it has a slightly flared bulb on the very bottom for durability.
The old Town Spruce paddle weighs 1 lb. 10 oz. and the maple paddle weighs only four ounces more. Judging by its age, it seems to be plenty sturdy enough (it's the paddle I use most of the time) and it actually balances slightly better than the Old Town, though both are quite good. If it was spruce or cedar, it would snap like a toothpick, but the dense, tough maple works great if you are willing to really thin it out in those places where bulk is just added weight.
I see a lot of very expensive, very fancy paddles at shows like Canoecopia, both solid and all sorts of fancy laminations. Unfortunately, many of them (including some of the most expensive) have terrible balance, especially if they have a lot of hardwood in them. If you pick up a well-balanced paddle with one hand by the lower grip area, as if you were going to use it, and you let it balance itself on your fingers, it should seek a horizontal position ALL BY ITSELF. The last thing you want to be doing all day is lifting the blade on every stroke. It should pivot on your lower hand, lifting the blade clear of the water without your help. In many ways, this well may be more important that the paddle's total weight in terms of how much energy you have to spend for an afternoon's paddling trip.
Whether you're talking about a traditional beaver-tail, a big, squared-off whitewater-style paddle or a modern bent shaft, they all can be, and should be, made to balance properly. So when you're looking for paddles, before you're blinded by all the fancy laminations or gorgeous finishes, pick up the paddle by the throat and let it sit there with a loose grip, balancing on just two fingers. This will tell you far more about the true quality of the paddle than your eyes will. If you're carving your own paddles, it will tell you if the blade has been thinned out enough.
This is also one of the reasons that a lot of oars have big, un-rounded upper shafts and Maine Guide-style canoe paddles tend to have large, long grips. The additional wood up there is acting like a counterweight to give them better balance.
